Perforated structure

Abstract

To suitably heat food stored in a microwave heating container.SOLUTION: The perforation structure includes a long hole group 40 comprised of multiple long holes 4 that penetrate a lid body 3 in the thick direction on a main part 31 extending planer-like of a lid body 3 that covers the opening of a container body that forms a microwave heating container in a bowl shape. Each of the long holes 4 of the long hole group 40 extends connecting between one point of a first circumference h1 that is the circumference of a first virtual circle V1 and one point of a second circumference h2 that is the circumference of a second virtual circle V2, and the clearance between outer ends 42 on the second circumference h2 on the long hole 4 is 3.5 mm or over, and the opening ratio, which is the percentage of the total of the areas of the regions that each of the long holes 4 penetrates against the denominator area that is an area where a donut-like annual region extends removing the first virtual circle V1 from the second virtual circle V2, is 12.0% to 47.5%.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a perforation structure having a group of long holes each of which penetrates a lid of a container for heating in a microwave oven. [Background technology]

[0002] Boxed lunches sold at convenience stores and supermarkets use containers that hold food to be heated in a microwave oven. In such containers for microwave heating, food is held in a bowl-shaped container body, and the opening of the container body is covered with a lid that can be attached and detached from the container body. When the food is to be heated, the container for microwave heating is heated in a microwave oven with the food held in the container body with the opening covered by the lid.

[0003] If the above-mentioned microwave heating container is sealed, the moisture contained in the food will evaporate during heating, and the internal pressure caused by the water vapor may cause the lid to come off the container body, which may result in the food being improperly heated. In view of this, a structure has been proposed in which a number of long holes are provided penetrating the lid of a container for microwave heating. With such a perforated structure, water vapor that evaporates from the moisture contained in food during heating can escape to the outside through the long holes (see Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-47953 A [Patent Document 2] JP 2020-172273 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, depending on the size of the opening through which the multiple long holes provided in the lid of the above-mentioned microwave heating container penetrate, there is a risk that water vapor will not be able to escape easily, causing the food to become sticky, or that excessive water vapor will be released, causing the food to dry out, and the food will not be heated properly. Thus, there is room for improvement in terms of properly heating food contained in a microwave oven heating container.

[0006] The perforation structure of the present invention was invented in consideration of the above problems, and one of its objectives is to properly heat food contained in a microwave oven heating container. However, other objectives of the present invention are not limited to this objective, and the effects and advantages derived from the respective configurations shown in the "Mode for Carrying Out the Invention" described later, which cannot be obtained by conventional techniques, can also be considered as another objective of the present invention. [Means for solving the problem]

[0007] The present inventors have thoroughly investigated the above-mentioned problems, and as a result, have found that food contained in a container for microwave heating can be appropriately heated as long as the size of the opening through which the multiple long holes penetrate provided in the container is within a predetermined range. Specifically, the following drilling structure was completed: This perforation structure is a container for microwave heating, and has a group of long holes that penetrate the thickness direction of the lid body in a main part that extends in a plane and covers the opening of a bowl-shaped container body.

[0008] One perforation structure disclosed here is based on the assumption that a first virtual circle having a first radius and a second virtual circle having a second radius larger than the first radius are two concentric circles in the main portion, and the group of long holes extends connecting a point on a first circumference that is the circumference of the first virtual circle and a point on a second circumference that is the circumference of the second virtual circle, the distance between the outer ends of the long holes on the second circumference is 3.5 mm or more, and the opening ratio, which is the percentage of the numerator area, which is the sum of the areas of the regions through which each of the long holes penetrates, to the denominator area, which is the area over which a donut-shaped ring region extends excluding the first virtual circle from the second virtual circle, is 12.0% or more and 47.5% or less. The aperture ratio is preferably 37.0% or less, and more preferably 12.5% ​​or more.

[0009] Another perforated structure disclosed herein is, under the assumption that a first virtual circle having a first radius and a second virtual circle having a second radius larger than the first radius are two concentric circles in the main portion, the group of long holes is a group of virtual long holes consisting of a plurality of virtual long holes extending connecting a point on a first circumference that is the circumference of the first virtual circle and a point on a second circumference that is the circumference of the second virtual circle, and has a shape enlarged or reduced in only one direction on a plane in which the main portion extends, the distance between outer ends of the long holes on a second virtual ellipse obtained by enlarging or reducing the second virtual circle in the one direction is 3.5 mm or more, and the opening ratio, which is a percentage of the numerator area, which is the sum of the areas of the regions through which each of the long holes penetrates, to a denominator area, which is the area over which a donut-shaped ring region extends, excluding the first virtual ellipse obtained by enlarging or reducing the first virtual circle in the one direction from the second virtual ellipse, is 12.0% or more and 47.5% or more. Effect of the Invention

[0010] According to the perforated structure of the present invention, food contained in the microwave oven heating container can be heated appropriately. [Brief description of the drawings]

[0011] [Figure 1] FIG. 2 is an exploded perspective view showing a microwave oven heating container having a perforated structure. [Diagram 2] 1 is an enlarged plan view showing the perforation structure of a main part of a container for microwave heating. FIG. [Diagram 3] FIG. 11 is a plan view (corresponding to FIG. 2) showing a perforation structure according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The perforation structure according to the present embodiment is a structure of holes formed in a microwave oven heating container (hereinafter, abbreviated as "container") that has a bowl-shaped container body and a lid body that covers the opening of the container body, which are detachably provided. In the following embodiments, directions are defined based on a state in which the container is placed on a horizontal surface. For example, the direction in which the lid is located relative to the container body is defined as "upward," and the opposite direction to "upward" is defined as "downward."

[0013] I. One embodiment In one embodiment below, the configuration of the perforation structure is described in items [1] and [2]. Item [1] outlines the container provided with the perforation structure, and item [2] describes the parameters of the perforation structure. Then, the actions and effects of the configurations of items [1] and [2] are described in item [3].

[0014] [1. Container] 1, the container 1 is provided with a bowl-shaped container body 2 that contains food 9 (heating target, contents) to be heated in a microwave oven, and a lid 3 that covers an opening 21 surrounded by an upper edge 20 of the container body 2. In this embodiment, an example in which an opaque container body 2 and a transparent lid 3 are used is given.

[0015] The container body 2 and the lid 3 are formed from a heat-resistant material that can withstand heating in a microwave oven. Examples of materials for the container body 2 and the lid 3 include resin materials such as polyethylene, polypropylene, polystyrene, polyethylene terephthalate, polylactic acid, and acrylic resin. The container body 2 and the lid 3 can be obtained by processing a sheet that mainly contains these resin materials. The "sheet" referred to here may be a sheet in which resin layers of different compositions are laminated, or may include a foamed resin sheet containing voids inside. The lid 3 can be obtained by processing such a sheet to match the shape of the opening 21 of the container body 2. The "processing" referred to here includes processing the above-mentioned sheet into a three-dimensional shape by hot pressing using a mold.

[0016] In this container 1, after food 9 is accommodated in the container body 2, the container body 2 and the lid body 3 are joined together. The container body 2 and the lid body 3 exemplified in this embodiment are three-dimensionally molded into uneven shapes that are detachable from each other. Specifically, the upper edge portion 20 of the container body 2 and the peripheral edge portion 30 of the lid body 3 are three-dimensionally molded into uneven shapes that are detachable from each other (detachable), and the container body 2 and the lid body 3 are joined to each other by this uneven shape.

[0017] In the attached state with the lid 3 attached to the container body 2, the opening 21 is covered by the lid 3, protecting the food 9 contained in the container body 2. If the container 1 is heated in a microwave oven in this attached state, the food 9 contained in the container body 2 can be heated. Hereinafter, the time when the container 1 is heated in the attached state with the lid 3 attached to the container body 2 containing the food 9 is simply referred to as "during heating". In addition, in the removed state where the lid body 3 is removed from the container body 2, the lid body 3 covering the opening 21 can be removed to open it, making it possible to eat the food 9 contained in the container body 2.

[0018] However, the container body 2 and the lid body 3 are not limited to being three-dimensionally molded into a detachable uneven shape, and may be joined by known joining means such as an adhesive, an adhesive tape, or a stapler. Alternatively, the container body 2 and the lid body 3 may be fixed (joined) to each other by a shrink film that covers the container body 2 and the lid body 3. When a thermoplastic resin is used as the material for the container body 2 and the lid body 3, the container body 2 and the lid body 3 may also be joined by a method of heat fusing (joining) the container body 2 and the lid body 3 by heat sealing them.

[0019] The container 1 has a perforated structure in which a long hole 4 (only one hole is indicated by a reference number in FIG. 1) is formed to connect the inside and outside of the container 1. The perforation structure is provided in the lid 3 because providing the perforation structure in the container body 2 in which the food 9 is stored may cause leakage of the food 9. This perforation structure is arranged in the main portion 31 of the lid 3 excluding the peripheral portion 30 because providing the perforation structure in the peripheral portion 30 of the lid 3 may cause a decrease in the joining and removability of the lid 3 to the container body 2.

[0020] The main portion 31 is a portion of the lid 3 that is surrounded by the peripheral portion 30 and extends in a plane. Fig. 1 illustrates the main portion 31 having a perfect circular (circular) shape in a plan view. However, the shape of the main part 31 in plan view (the general shape of the lid body 3) is not limited to a perfect circle, and may be an elliptical circle, a rectangle, or a polygon with five or more sides. Examples of the shape of the main part 31 that is a rectangle in plan view include a square, a rectangle, a diamond, and a trapezoid. In other words, various shapes are applicable to the general shape of the container 1 in plan view.

[0021] The perforation structure provided in the main portion 31 includes a group of elongated holes 40 each consisting of a plurality of elongated holes 4. The elongated holes 4 constituting the group of elongated holes 40 are holes that penetrate the main portion 31 (the cover body 3) in the thickness direction and extend along the extending plane of the main portion 31, and when the number of the elongated holes is "n", the group of elongated holes 4 has an n-fold rotationally symmetric shape. As a specific example, a group of elongated holes 4 having eight elongated holes 4 has eight-fold symmetry.

[0022] As shown in Fig. 2, each of the elongated holes 4 penetrates through the main part 31 so as to straddle two virtual circles V1 and V2. The virtual circles V1 and V2 mentioned here are concentric true circles (concentric circles) sharing the center C, and the other second virtual circle V2 is larger than one first virtual circle V1. That is, if the radius of the first virtual circle V1 is the first radius r1 and the radius of the second virtual circle V2 is the second radius r2, the inequality "r1 < r2" holds.

[0023] Each elongated hole 4 extends by connecting the circumference of the first virtual circle V1 (hereinafter referred to as the "first circumference") h1 and the circumference of the second virtual circle V2 (hereinafter referred to as the "second circumference") h2. Specifically, in each elongated hole 4, one end portion (hereinafter referred to as the "inner end portion") 41 on the center C side is arranged on the first circumference h1, and the other end portion (hereinafter referred to as the "outer end portion") 42 on the side opposite to the center C is arranged on the second circumference h2. In other words, each of the elongated holes 4 extends by connecting a point on the first circumference h1 and a point on the second circumference h2. From this, it can be said that the first virtual circle V1 is a circle (circumscribed circle) circumscribing each of the elongated holes 4, and the second virtual circle V2 is a circle (inscribed circle) inscribed in each of the elongated holes 4.

[0024] In this embodiment, an example is shown in which the end portions 41 and 42 of the elongated hole 4 are provided in a semi-circular shape, and the portion excluding the end portions 41 and 42 is provided in a long-side rectangular shape with the diameter of the end portions 41 and 42 as the short side (width). Also, Fig. 2 shows an example in which each of the elongated holes 4 extends linearly with a slight inclination with respect to the extending direction of the radii r1 and r2. However, each of the elongated holes 4 may extend along the radial direction, or may extend in various shapes such as an arc shape, a sine wave shape, a triangular wave, and a rectangular wave.

[0025] In the following description, the radial direction and the circumferential direction are defined based on the center C. The radial direction is the direction in which the radii r1 and r2 extend, and the direction in which the tangent of the circle having the radii r1 and r2 extends (the direction perpendicular to the radial direction) is the circumferential direction. The perforation structure provided with the elongated hole group 40 composed of the above-mentioned elongated holes 4 has the following parameters to be described.

[0026] [2.Parameter] In this section [2], the following parameters a to g will be sequentially explained with respect to the long hole 4 of the long hole group 40 provided as the perforation structure. Parameter a: Radii r1 and r2 of virtual circles V1 and V2 Parameter b: Inclination angle θ of slot 4 relative to the radial direction Parameter c: The longitudinal and transverse dimensions L and W of the long hole 4 Parameter d: Number of slots 4 n Parameter e: Distance between long holes 4 D1, D2 Parameter f: Area S of slot 4 Parameter g: aperture ratio R

[0027] <Radius r1, r2 of imaginary circles V1, V2> The first radius r1 of the first virtual circle V1 is preferably equal to or larger than a predetermined first lower limit radius r11 from the following viewpoint A, and is preferably equal to or smaller than a predetermined first upper limit radius r12 from the following viewpoints B and C. Point A: To ensure the machining accuracy of the long hole 4 Point of view B: A point of view for ensuring the extension range of the long hole 4 in the main portion 31 (From the viewpoint of ensuring aperture ratio R) Point C: The long hole 4 is as far away from the peripheral edge 30 as possible in the main portion 31. The perspective of centering

[0028] The above viewpoint B can also be rephrased as the following viewpoints B1 and B2. Point of view B1: When heated, steam is not easily discharged from the long hole 4, so that the inside of the container 1 It is safe because it prevents the lid 3 from coming off the container body 2 due to excessive pressure. Perspective for improving Point B2: The steam generated during heating is difficult to be discharged from the long hole 4. Water vapor condenses inside the body 3, and the water droplets fall onto the food 9. From the viewpoint of suppressing deterioration of the texture of food 9 (steaming food 9 properly) (perspective)

[0029] The above viewpoint C can also be rephrased as the following viewpoints C1 and C2. These viewpoints C, C1, and C2 can also be said to be viewpoints for preventing a user of the container 1 (hereinafter simply referred to as a "user") from getting burned. Viewpoint C1: Steam passing through the long hole 4 is concentrated near the center of the lid 3 to form a steam column. The viewpoint of exposing the problem and alerting users not to engage in the crime Viewpoint C2: Water vapor is released to the hand of the user lifting the upper edge 20 of the container body 2. From the viewpoint of keeping a distance from the long hole 4 where water may be discharged

[0030] The first lower limit radius r11 is preferably 1.0 [mm], more preferably 2.0 [mm], and even more preferably 3.0 [mm]. The second upper limit radius r12 is preferably 7.0 [mm], more preferably 6.0 [mm], and even more preferably 5.0 [mm]. In other words, with respect to the first virtual circle V1, the inner area A1 of the area corresponding to the area of ​​the first virtual circle V1 is preferably greater than or equal to a first lower limit area A11 (specifically, "pi × r11 × r11") corresponding to the first lower limit radius r11, and is preferably less than or equal to a first upper limit area A12 (specifically, "pi × r12 × r12") corresponding to the first upper limit radius r12.

[0031] The first radius r2 of the second virtual circle V2 is preferably equal to or greater than a predetermined second lower limit radius r21 from the above viewpoint B, and is preferably equal to or smaller than a predetermined second upper limit radius r22 from the above viewpoint C and the following viewpoint D. Perspective D: Ensuring design The above viewpoint D can be said to be a viewpoint that by providing a transparent portion in the main portion 31 instead of the slot 4, the food 9 can be easily viewed (observed) from the outside.

[0032] The second lower limit radius r21 is preferably 7.0 [mm], more preferably 8.0 [mm], and even more preferably 9.0 [mm]. The second upper limit radius r22 is preferably 20.0 [mm], more preferably 18.0 [mm], and even more preferably 16.0 [mm].

[0033] In other words, with respect to the second virtual circle V2, the outer area A2 of the area corresponding to the area of ​​the second virtual circle V2 is preferably greater than or equal to a second lower limit area A21 corresponding to the second lower limit radius r21 (specifically, "pi × r21 × r21"), and is preferably less than or equal to a second upper limit area A22 corresponding to the second upper limit radius r22 (specifically, "pi × r22 × r22"). The area of ​​the main portion 31 on which the imaginary circles V1 and V2 are formed is the area (so to speak) of the area extending in a plane. The area of ​​the container 1 that mainly covers the opening 21 is set to 70 cm in order to ensure the capacity of the container 1. 2 ] or more, and from the size required for the container 1, it is preferable that the thickness is within 1000 [cm 2 ] or less.

[0034] <Inclination angle θ of the long hole 4 with respect to the radial direction> The inclination angle θ of the slot 4 with respect to the radial direction can be any angle in the range of 0° or more and 90° or less. From the viewpoint B above, the larger the angle, the better, but from the viewpoint E below, the smaller the angle, the better. Point E: The water vapor from the water contained in the food 9 evaporates through the slot 4 during heating. From the viewpoint of preventing problems caused by excessive discharge to the outside of the container 1

[0035] This viewpoint E can also be rephrased as the following viewpoints E1 and E2. Point of view E1: The food 9 is heated by suppressing the excessive evaporation of water contained in the food 9. Prevent food from drying out and secure moisture (and therefore commercial value) Perspective Point of view E2: Evaporation of water vapor from the container 1 through the long hole 4 during heating. From the viewpoint of preventing burns In addition, the larger the inclination angle θ, the more easily the flow of water vapor escaping to the outside of the container 1 swirls in a vortex shape, and the less likely the water vapor is to dissipate to the outer periphery of the slot 4. Therefore, from the viewpoint E2 above, the larger the inclination angle θ, the more preferable it is.

[0036] <Longitudinal and lateral dimensions L, W of long hole 4> With regard to the longitudinal and lateral dimensions L and W of the slot 4, the longitudinal dimension L is the length of the slot 4 extending along the direction at the inclination angle θ with respect to the radial direction, and the lateral dimension W is the width of the slot 4 along a direction perpendicular to the radial direction at the inclination angle θ. The larger these dimensions L and W are, the more easily water vapor produced by evaporation of moisture contained in food 9 can escape to the outside of container 1 through slot 4 when heated.

[0037] The longitudinal dimension L is preferably equal to or greater than a predetermined longitudinal lower limit dimension L1 from the above viewpoints A and B, and is preferably equal to or less than a predetermined longitudinal upper limit dimension L2 from the above viewpoints C and E. Moreover, the transverse dimension W is preferably equal to or greater than a predetermined transverse lower limit dimension W1 from the above viewpoints A and B, and is preferably equal to or less than a predetermined transverse upper limit dimension W2 from the above viewpoint E and the following viewpoint F. Point of view F: Point of view to prevent foreign matter from entering from the outside to the inside through the long hole 4

[0038] The above-mentioned viewpoint F, in the case of a long hole structure larger than a specified upper longitudinal dimension L2, can also be said to be a viewpoint that suppresses the intrusion of foreign matter from the outside by the water vapor passing through the long hole 4 when heated, pushing up the edges of the long hole 4 and expanding the short-side dimension W of the long hole 4. On the other hand, it is also preferable that the predetermined lower longitudinal limit dimension L1 is set from the following viewpoint G. This is because, with a longitudinal dimension L smaller than the predetermined lower longitudinal limit dimension L1, a large number of elongated holes 4 are required to ensure an aperture ratio R, the details of which will be described later, and arranging the large number of elongated holes 4 close to each other may result in a lack of strength of the main portion 31 (lid body 3). Point of view G: To ensure the strength of the main part 31

[0039] The lower longitudinal limit dimension L1 is preferably 8.0 mm, more preferably 10.0 mm, and even more preferably 12.0 mm, in order to ensure the aperture ratio R and from viewpoint G. The upper longitudinal limit dimension L2 is preferably 24.0 mm, more preferably 22.0 mm, and even more preferably 20.0 mm, in order to ensure the aperture ratio R and from viewpoint F. The lower limit of the short side dimension W1 is preferably 0.2 mm, more preferably 0.3 mm, and even more preferably 0.4 mm. The upper limit of the short side dimension W2 is preferably 0.9 mm, particularly from viewpoint F, more preferably 0.8 mm, and even more preferably 0.7 mm.

[0040] The longitudinal dimension L of the long hole 4 is geometrically determined by the above-mentioned "first radius r1", "first radius r2" and "inclination angle θ". Therefore, it can be said that the length of the longitudinal dimension L of the long hole 4 can be adjusted by the numerical values ​​applied to the "first radius r1", "first radius r2" and "inclination angle θ". In other words, the four parameters of "first radius r1", "first radius r2", "inclination angle θ" and "longitudinal dimension L of the long hole 4" can be set by the numerical values ​​applied to the other three parameters. The magnitude of any two of these four parameters can also be adjusted (set) by the numerical values ​​applied to the other two parameters.

[0041] <Number of long holes 4 n> The number n of the long holes 4 is preferably equal to or larger than a predetermined lower limit number n1 from viewpoint B above, and is preferably equal to or smaller than a predetermined upper limit number n2 from viewpoint A and viewpoint G above. The lower limit number n1 is preferably 4, more preferably 6, and even more preferably 8. The upper limit number n2 is preferably 20, more preferably 18, and even more preferably 16.

[0042] <Spacing between long holes 4 D1, D2> The intervals D1, D2 between the long holes 4 are the dimensions separating predetermined points on each of the circumferentially adjacent long holes 4. These intervals D1, D2 include a first interval D1 which is the shortest distance separating the long holes 4, and a second interval D2 separating the outer ends 42 of the long holes 4. An example of the first interval D1 is the dimension separating the inner ends 41 of the long holes 4.

[0043] Since the intervals D1, D2 between the oblong holes 4 tend to become narrower as the number n of the oblong holes 4 increases, it is preferable that the upper and lower limits be set from the same viewpoint as the number n. Specifically, the first interval D1 is preferably equal to or larger than the predetermined first lower limit interval D11 from the above viewpoint A and the above viewpoint G, and is preferably equal to or smaller than the predetermined first upper limit interval D12 from the above viewpoint B. Similarly, the second interval D2 is preferably equal to or larger than the predetermined first lower limit interval D21 from the above viewpoint A and the above viewpoint G, and is preferably equal to or smaller than the predetermined first upper limit interval D22 from the above viewpoint B.

[0044] More specifically, with regard to a perforation structure in which the first interval D1 is less than the first lower limit interval D11, it is difficult to ensure sufficient strength of the main portion 31 (lid body 3) to withstand the pressure of steam passing through the slots 4 during heating, and there is a risk that adjacent slots 4 in the circumferential direction will be connected to each other (the portions between the slots 4 will be damaged). Holes in which the slots 4 are connected to each other in this way (i.e., rolled-up openings) may lead to excessive discharge of steam. Therefore, it can be said that the larger the first lower limit interval D11 of the first interval D1, the more preferable it is from the viewpoint E2 above.

[0045] Furthermore, in the case of a perforated structure in which the second interval D2 is less than the second lower limit interval D21, the density of water vapor passing through the slots 4 at the second circumference h2 of the second imaginary circle V2 increases during heating. This excessive concentration of water vapor discharged from the outer ends 41 of the slots 4 may result in burns when the user places their hands over the second circumference h2. Therefore, it can be said that the larger the second lower limit interval D21 of the second interval D2, the more preferable it is from the viewpoint E2 described above.

[0046] The first lower limit distance D11 is preferably 0.3 mm, more preferably 0.6 mm, and even more preferably 0.9 mm. The first upper limit distance D12 is preferably 2.8 mm, more preferably 2.5 mm, and even more preferably 2.2 mm. The second lower limit distance D21 is preferably 3.5 mm, more preferably 3.8 mm, and even more preferably 4.0 mm. The second upper limit distance D22 is preferably 8.5 mm, more preferably 8.0 mm, and even more preferably 7.5 mm.

[0047] The distances D1, D2 between the long holes 4 are geometrically determined by parameters such as the above-mentioned "radii r1, r2," "number n," and "dimensions L, W." Therefore, the length of the distances D1, D2 can be adjusted by the numerical values ​​applied to each of these parameters. In this way, the magnitude of some of the multiple parameters related to each other can be adjusted (set) by the magnitude of other parameters.

[0048] <Area S of long hole 4> The area S of the long holes 4 is the total opening area (=n×L×W) of the long holes 4, calculated by multiplying the "longitudinal dimension L" and the "transverse dimension W" of the long holes 4, and multiplying the opening area of ​​each of the long holes 4 by the number n of the long holes 4. In this way, the area S, which is the sum of the areas of the regions penetrated by the long holes 4, is preferably equal to or larger than a predetermined lower limit area S1 from the above viewpoint B, and is preferably equal to or smaller than a predetermined upper limit area S2 from the above viewpoints D, E, and G.

[0049] The lower limit area S1 is 5.0 mm 2 ], and 6.0 [mm 2 ] is more preferable, and 7.0 [mm 2 The upper limit area S2 is preferably 14.0 mm 2 ], and 13.0 [mm 2 ] is more preferable, and 12.0 [mm 2 It is even more preferable that The size of the area S of the long hole 4 is determined according to the "longitudinal dimension L" and "transverse dimension W" of the long hole 4 and the "number n" of the long holes 4. Therefore, the size of the area S can be adjusted according to the values ​​applied to these dimensions L, W and the number n.

[0050] <Aperture ratio R> The aperture ratio R is a percentage of the area S of the slot 4 to the denominator area SA, which is the area of ​​the donut-shaped annular region A3 obtained by excluding the inner region A1 from the outer region A2. The denominator area SA is the area obtained by subtracting the area SA1 of the first imaginary circle V1, which forms the area of ​​the inner region A1, from the area SA2 of the second imaginary circle V2, which forms the area of ​​the outer region A2. Therefore, the aperture ratio R is calculated by the formula "(S / SA) x 100".

[0051] The opening rate R is set to a predetermined lower limit opening rate R1 and an upper limit opening rate R2 based on the viewpoint of appropriately heating the food 9 contained in the container body 2. Specifically, the opening rate R is preferably equal to or greater than the predetermined lower limit opening rate R1 from the viewpoints B and G above, and is preferably equal to or less than the predetermined upper limit opening rate R2 from the viewpoints D and E above.

[0052] The lower limit aperture ratio R1 is preferably 12.0% and more preferably 12.5% ​​and even more preferably 13.0%. The upper limit aperture ratio R2 is preferably 47.5% and even more preferably 42.0% and, particularly from viewpoint E, even more preferably 37.0%. The aperture ratio R can be adjusted by changing the values ​​applied to the above-mentioned parameters related to the areas S and SA (specifically, "radius r1, r2," "inclination angle θ," "dimension L, W," "number n," and "spacing D1, D2").

[0053] [3. Actions and Effects] Since the perforation structure of this embodiment has the configuration described above, the food 9 contained in the container body 2 can be heated appropriately. Specifically, the perforated structure exemplified in this embodiment has a predetermined second lower limit distance D21 related to the second interval D2 of 3.5 [mm], and a predetermined lower limit opening rate R1 related to the opening rate R of 12.0 [%] and a predetermined upper limit opening rate R2 of 47.5 [%] (i.e., the opening rate R is 12.0 [%] or more and 47.5 [%] or less). With this perforated structure, by heating the container 1 in a microwave oven, the food 9 can be appropriately steamed while preventing the food 9 from drying out, and the user can be prevented from getting burned. Furthermore, a perforated structure in which the predetermined upper limit opening rate R2 related to the opening rate R is 37.0% (i.e., the opening rate R is 37.0% or less) can improve the effect of preventing the food 9 from drying out while also improving the effect of preventing the user from getting burned. A perforated structure in which the predetermined lower limit opening rate R2 related to the opening rate R is 12.5% ​​(i.e., the opening rate R is 12.5% ​​or more) can more appropriately steam the food 9.

[0054] [II. Examples] The present invention will be specifically described below with reference to examples and comparative examples relating to the perforated structure provided in the container, although the present invention is not limited to the following examples. In this section II, the perforation structures of Examples 1 to 30 and Comparative Examples 1 to 20 shown in Tables 1 to 6 below will be described. The long holes provided in each of the perforation structures of Examples 1 to 30 and Comparative Examples 1 to 20 are all linear, with the inner and outer ends each being semicircular. Tables 1 to 6 also include the symbols used in the parameters described above in one embodiment (specifically, the symbols for "radius r1, r2," "inclination angle θ," "dimension L, W," "number n," "distance D1, D2," and "aperture ratio R").

[0055] [Table 1]

[0056] [Table 2]

[0057] [Table 3]

[0058] [Table 4]

[0059] [Table 5]

[0060] [Table 6]

[0061] For the containers used in Examples 1 to 30 and Comparative Examples 1 to 20 shown in Tables 1 to 6, the following container bodies and lids were used. Container body: Polypropylene resin skin layer on both sides of foamed polypropylene resin layer A resin sheet having a thickness of 2 mm and a diameter of 20 mm was heat-pressed. A container body having a circular bottom of 7 cm and a depth of 7 cm was prepared. Lid: A 0.5mm thick polystyrene resin sheet is heat pressed. A circular lid having a size that matches the container body was obtained. Furthermore, the upper edge of the container body and the peripheral edge of the lid were heat-pressed to form projections and recesses that could be fitted together (joined) with each other. Then, perforated structures having parameters shown in Examples 1 to 30 and Comparative Examples 1 to 20 shown in Tables 1 to 6 were formed by a laser.

[0062] The first distance D1 was measured by the following method X. Measurement method X: The line segment connecting the edge of one slot to the edge of the adjacent slot is the shortest. Find the line segment by measuring with a ruler, and measure the length of the line segment with the long hole. The shortest distance was determined as the distance between the holes. All the holes in the group were measured in the same way. The average value was calculated, and this calculation result was used as the first interval D1.

[0063] In addition, the second distance D2 was measured by the following method Y. Measurement method Y: A point where the edge of one long hole and the circumference of the second imaginary circle are in contact with each other, and this long hole and the point where the edge of the adjacent slot and the circumference of the second imaginary circle meet. The straight-line distance was measured with a ruler. The same measurement was carried out for all the long holes. The average value is calculated and the result is used as the second interval D2. Ta.

[0064] For each of Examples 1 to 30 and Comparative Examples 1 to 20, an evaluation was performed to see whether food could be properly heated when the container was heated in a microwave oven with the lid attached to the container body containing food. Here, the proper heating of food was evaluated based on three items: the steaming effect of food, the effect of preventing partial drying of food, and the effect of preventing burns to the user.

[0065] These three evaluation items have in common that 180 g of cooked rice that had been cooled to 8°C was placed into the container body, the lids of Examples 1 to 30 and Comparative Examples 1 to 20 were fitted (joined), and the containers were heated for 1 minute in a microwave oven with an output of 600 W (i.e., containers containing reheated food). The contents used for the evaluation of each item are described below. In addition, each evaluation item was evaluated on a three-level scale: good (marked with "○" in the table), fair (marked with "△" in the table), and poor (marked with "×" in the table).

[0066] The effect of steaming food and the effect of preventing partial drying of food were evaluated using a questionnaire as follows. Evaluation method: Five subjects tasted the rice contained in the container to be evaluated. The steaming effect of rice (food) and the partial prevention of drying We conducted a survey about each of these.

[0067] In the questionnaire on the steaming effect, each subject gave a score based on the following criteria. 4 points: The rice is fluffy. 3 points: The rice is warm enough. 2 points: The rice feels unevenly heated. Or it may be sticky in some areas. 1 point: The rice wasn't warm enough. Or the rice is sticky.

[0068] In addition, in the questionnaire regarding the effect of preventing localized dryness, each subject gave a score according to the following criteria. 4 points: The rice is moist throughout. 3 points: There are some areas where the rice feels a little low in moisture. 2 points: There are some areas where the rice feels low in moisture. 1 point: There are some areas where the rice is clearly low in moisture.

[0069] The steaming effect and the effect of preventing localized dryness were evaluated according to the following criteria, based on the total scores given by five subjects. Good: 17 points or more (marked as "○" in the table) Pass: 14 points or more but less than 17 points (marked as "△" in the table) -Fail: Less than 14 points (marked as "x" in the table)

[0070] The effectiveness of the product in preventing burns to users was evaluated using the following method. Evaluation method: Immediately after heating the evaluation object, the container was placed 10 cm above the long holes. Between the two grammage 48 [g / m 2 ] high-quality paper is tilted 45[°] and held up horizontally. Thermography camera (product name: R500, Nippon Avio) Nix Co., Ltd.) and the surface temperature of the high-quality paper is 65 degrees or higher. and the surface temperature of the surrounding area is less than 65[℃] and more than 45[℃] Visualize the area vertically above the slots in the wood-free paper. On a straight line from the center to the outer periphery, the surface temperature of the wood-free paper reaches 65°C. The point where the surface temperature of the fine paper drops to 45[℃] The distance between the two was calculated, and the evaluation was based on this distance.

[0071] The burn prevention effect according to the distance calculated by the above evaluation method was evaluated according to the following criteria. Good: The separation distance is 3 cm or more. Acceptable: The separation distance is less than 3 cm and greater than or equal to 2 cm. - Not acceptable: The separation distance is less than 2 cm.

[0072] The area above 65°C can be treated as an area where a user may be burned when he or she places his or her hand in it. Furthermore, the area above 45°C but below 65°C can be treated as an area where a user may feel hot when he or she places his or her hand in it, but may be able to quickly move the hand away from the container without being burned for a short period of time. Therefore, the above evaluation criteria are adopted based on the knowledge that the longer the distance between the position where the temperature drops to 65°C and the position where the temperature drops to 45°C on the fine paper used to evaluate the burn prevention effect, the higher the burn prevention effect.

[0073] In Examples 1 to 30, the second distance D2 is 3.5 mm or more, and the aperture ratio R is 12.0% or more and 47.5% or less. In these Examples 1 to 30, the effect of steaming food, the effect of preventing partial drying of food, and the effect of preventing burns to the user were rated at least "fair" or better.

[0074] On the other hand, in Comparative Examples 2 to 7 and 10 to 20, which had an aperture ratio R of less than 12.0%, the steaming effect was evaluated as "fail." From this, it is presumed that with a perforation structure with an aperture ratio R of less than 12.0%, steam generated during heating is difficult to discharge from the long holes, and water droplets formed by condensation of steam inside the lid fall onto the food, degrading the texture of the food.

[0075] In addition, in Comparative Examples 1, 8, and 9, in which the opening rate R was greater than 47.5%, not only was the steaming effect rated as "poor", but the partial drying prevention was also rated as "poor". From this, it is presumed that with a perforation structure with an opening rate R greater than 47.5%, the moisture contained in the food is excessively discharged to the outside of the container when heated, making it impossible to steam the food properly and preventing the food from drying out.

[0076] In Comparative Examples 1 and 9, in which the opening rate R was greater than 60.0% and the second interval D2 was less than 3.5mm, the steaming effect and partial drying prevention were rated as "Fail", and the burn prevention effect was also rated as "Fail". From this, it is presumed that a perforated structure in which the second interval D2 is less than 3.5mm or the opening rate R is greater than 60.0% may cause burns to the user due to steam escaping to the outside of the container through the long holes when heated.

[0077] In the light of Comparative Examples 1 to 20, the perforated structures of Examples 1 to 30 have a configuration in which the second interval D2 is 3.5 [mm] or more and the aperture ratio R is 12.0 [%] or more and 47.5 [%] or less. In other words, the perforated structures of Examples 1 to 30 have a configuration in which the aperture ratio R is set in a predetermined range of 12.0 [%] or more and 47.5 [%] or less, on the premise that the second interval D2 is 3.5 [mm] or more. The perforated structure having such a configuration can achieve all of the steaming effect, partial drying prevention, and burn prevention effects.

[0078] Among Examples 1 to 30, in Examples 2 to 7, 9 to 22, and 24 to 30 in which the opening ratio R is 12.5% ​​or more and 37.0% or less, the steaming effect, partial drying prevention, and burn prevention effects were all evaluated as "good". On the other hand, in Examples 8 and 23 in which the opening ratio R is greater than 37.0% the steaming effect was evaluated as "good", but the partial drying prevention and burn prevention effects were evaluated as "passable". Comparing these Examples, it can be seen that the perforated structure with an opening ratio R of 37.0% or less has a high partial drying prevention and burn prevention effect. In Example 1 in which the opening ratio R is less than 12.5% ​​the partial drying prevention and burn prevention effects were evaluated as "good", but the steaming effect was evaluated as "passable". Comparing these Examples, it can be seen that the perforated structure with an opening ratio R of 12.5% ​​or more has a high steaming effect.

[0079] [III. Modifications] The above-described embodiment is merely an example, and is not intended to exclude various modifications and application of techniques not explicitly stated in the embodiment. Each configuration of the present embodiment can be modified in various ways without departing from the spirit of the embodiment. In addition, the configurations can be selected as necessary, and can be combined appropriately.

[0080] For example, in one embodiment, the present invention is not limited to the perforation structure having a plurality of long holes 4 extending across the perfect virtual circles V1 and V2 as described above, but may also use a perforation structure having a modified shape in which the perforation structure is compressed in one direction in a planar view. In the perforation structure according to the modified example, a group of imaginary elongated holes (i.e., the group of elongated holes 40 described above in one embodiment) consisting of a plurality of imaginary elongated holes (i.e., the elongated holes 4 described above in one embodiment) extending while connecting points on the circumferences h1, h2 of the imaginary circles V1, V2 described above in one embodiment, is formed in a shape enlarged or reduced in only one direction on a plane in which the main portion 31 extends. That is, in the perforation structure according to the modified example, as shown in Fig. 3, each elongated hole 4' extends while connecting a point on a first elliptical circumference h1' of a first imaginary ellipse V1' obtained by enlarging or reducing the first imaginary circle V1 in one direction and a point on a second elliptical circumference h2' of a second imaginary ellipse V2' obtained by enlarging or reducing the second imaginary circle V2 in one direction.

[0081] As described above, the following modified examples were evaluated with regard to the perforation structure in which a group of long holes 40' is provided in the main portion 31 (cover body 3), the group having a plurality of long holes 4' whose inner ends 41' are positioned on the first elliptical circumference h1' and whose outer ends 42' are positioned on the first elliptical circumference h2'. The modified example differs from Example 5 only in that the perforated structure of Example 5 is compressed to 60% of its length in only one direction in plan view, and was evaluated in the same manner as the above-mentioned examples. The modified example has a geometric second interval of 3.5 mm or more, and an opening ratio of 15.7%, which is the same as Example 5. This modified example was evaluated as "good" in all three aspects, steaming effect, partial drying prevention, and burn prevention effect, as in Example 5. Therefore, even with the perforated structure according to the modified example, the food contained in the container body can be properly heated. [Explanation of symbols]

[0082] 1 Container (container for microwave heating) 2 Container body 20 Upper edge 21 Aperture 3 Lid 30 Periphery 31 Main Section 4 long hole 40 Long hole group 41 Inner end 42 Outer end 9 Food C center D1 First interval D2 Second interval h1 First circumference h2 Second circumference r1 first radius r2 second radius V1 First virtual circle V2 Second virtual circle θ Tilt angle

Claims

1. A perforated structure in which a group of long holes consisting of a plurality of long holes penetrating in a thickness direction of a lid body is provided in a main part extending in a plane of a lid body covering an opening of a bowl-shaped container body in a microwave oven heating container, assuming that a first imaginary circle having a first radius and a second imaginary circle having a second radius larger than the first radius are two concentric circles in the main portion, the group of long holes extends so as to connect a point on a first circumference that is the circumference of the first imaginary circle and a point on a second circumference that is the circumference of the second imaginary circle, the distance between outer ends of the long holes on the second circumference is 3.5 mm or more, The first radius is 3.0 mm or more and 5.0 mm or less, The second radius is 9.3 mm or more and 15.9 mm or less, an opening ratio, which is a percentage of a numerator area, which is a sum of areas through which the long holes penetrate, to a denominator area, which is an area over which a doughnut-shaped ring region obtained by subtracting the first virtual circle from the second virtual circle extends, is 12.0% or more and 47.5% or less; A perforated structure characterized by:

2. The aperture ratio is 37.0% or less. The perforated structure according to claim 1 .

3. The aperture ratio is 12.5% ​​or more. The perforated structure according to claim 1 or 2.

4. A perforated structure in which a group of long holes consisting of a plurality of long holes penetrating in a thickness direction of a lid body is provided in a main part extending in a plane of a lid body covering an opening of a bowl-shaped container body in a microwave oven heating container, Assuming that a first imaginary circle having a first radius and a second imaginary circle having a second radius larger than the first radius are two concentric circles in the main portion, the group of long holes is a group of imaginary long holes each of which extends connecting a point on a first circumference that is the circumference of the first imaginary circle and a point on a second circumference that is the circumference of the second imaginary circle, and has a shape that is expanded or reduced in only one direction on a plane in which the main portion extends, and the distance between outer ends of the second imaginary circle in the long holes on a second imaginary ellipse expanded or reduced in the one direction is 3.5 mm or more, The first radius is 3.0 mm or more and 5.0 mm or less, The second radius is 9.3 mm or more and 15.9 mm or less, an opening ratio, which is a percentage of a numerator area, which is the sum of areas through which the long holes penetrate, to a denominator area, which is an area over which a donut-shaped ring region extends, obtained by excluding a first virtual ellipse obtained by enlarging or reducing the first virtual circle in one direction from the second virtual ellipse, is 12.0 [%] or more and 47.5 [%] or more; A perforated structure characterized by:

Images